coats

On 29.12.03, to the 8^th stand MC 250-3 there was mounted a set of rolls 42p-66 (350 mm in diameter) bored out with 6 calibres to roll the rhomb 40 x 6 mm.

The 1^st calibre (numerated from the input) has not been hardened, 2^nd and 3^rd calibres have been hardened by microplasma coating, and 4-6^th calibres have been hardened by discrete coating.

The rolling was began with the 5^th calibre; it was in operation 3 days from 29.12.03 to 1.01.04 and rolled 3754 tons without any claims. Then we transited to the 6^th calibre.

The 6^th calibre was in operation 2 days from 1.01.04 to 3.01.04 and rolled 2238 tons; a longitudinal crack has been revealed on both rolls; then we transited to the 4^th calibre.

The 4^th calibre was in operation 3 days from 3.01.04 to 6.01.04 and rolled 3115 tons.

Having measured with the template the wear-out of 5^th calibre, we decided as an experiment to put this calibre into further operation. The calibre was in operation from 6.01.04 to 7.01.04 and rolled additionally 1470 tons. Totally this calibre has rolled 5224 tons.

After this additional work of 5^th calibre, we transited to the 1^st calibre; it was in operation 2 days from 7.01.04 to 9.01.04 and rolled 1916 tons.

2^nd calibre (that worked from 9.01.04 to 11.01.04) has rolled 1904 tons.

3^rd calibre (that worked from 11.01.04 to 13.01.04) has rolled 1670 tons.

After this set has completed its term, we have measured the wear-out of calibres, see the sketches of wear-out in the appendix.

The maximal wear-out of 4^th, 5^th and 6^th calibres hardened by the discrete coating was -1,0 mm, and on the 1^st, 2^nd and 3^rd calibres not hardened by the discrete coating it amounted -1,5 mm. Thus, calibres hardened by the discrete coating have been worn out 0,67 times less, and the large grid of carbon deposit is absent on them.

The maximal value of resistance of calibres hardened by discrete coating amounted 5224 tons. Maximal value of resistance of non-hardened calibres was 1916 tons.

5224 tons : 1916 tons = 2,77 times,

i.e., the maximal resistance of calibre hardened by discrete coating is 2,77 times higher than maximal resistance of calibres that were not hardened by this technique.

Proceeding from the carried out testing and above calculation, we made the following conclusion:

the experimental calibres hardened by the suggested technique have an uniform wear-out;
during the operation time, the calibres wear out in proportion to the amount of rolled metal;
the maximal resistance of these calibres is 2,77 times more than that of calibres without this coating;
the surface of experimental calibres after operation has less grid of carbon deposit.